Short-distance dispersal occurs through water or rain splash (especially wind-driven rain) and human activities such as pruning. New lesions and spores can be produced within a single week under favorable conditions. The fungus can penetrate the leaf through the cuticle or enter through leaf stomata. Although infection can occur with 8 hours of wetness, dry breaks of 3 hours or more during wet periods resulted in less disease development. Only young leaves became infected at 54☏ but needed to be wet for 48 hours.
BLIGHT SYNONYM FREE
High humidity levels or free water are needed in order for infection to occur. Infection can occur very quickly in warm (64☏ to 77☏), wet conditions. Microsclerotia (long-lived survival structures) are formed within infected tissue, released into the soil when the tissues break down, and subsequently initiate new infections by producing infective spores or when splashed onto foliage directly. Mild wet weather west of the Cascade Range is conducive for long-term survival and infection. The fungus can survive in fallen leaves for up to 5 years and can produce spores in a sticky, slimy matrix when environmental conditions become suitable. sempervirens), 'Dee Runk', 'Green Gem', 'Green Mountain', 'Green Velvet', 'Suffruticosa', and 'Winter Gem'. In Oregon nurseries, the fungus was isolated from 20 different cultivars and frequently found on common boxwood ( B.
japonica 'Green Beauty' to be tolerant although they still carry the fungus. japonica (Japanese boxwood) are also hosts. insularis (Korean boxwood)-are known hosts. The three main boxwood species- Buxus sempervirens, B. and cultivars, Pachysandra, and Sarcococca. Due to the history of this disease, its explosive life cycle, and subtle symptoms on tolerant plants, it is expected to be an ever-increasing problem throughout the PNW. Plants that are tightly spaced in flats, grown pot-to-pot, or other spacing where plant canopies touch each other are also at risk for more severe disease. This includes plants in propagation greenhouses, those watered too frequently without sufficient time to dry between irrigation events, or are shaded by taller plants or structures. In nurseries, boxwood blight is severe in situations where there is high humidity or where moisture remains on leaves for long periods of time. The disease is especially severe in the landscape where plants are sheared tightly and/or planted in hedges. Calonectria henricotiea is an important species found only in Europe that is resistant to many fungicides. It has been a problem for many years in Europe and New Zealand. boxwood blight outbreaks is of only one major DNA type and is significantly differentiated from the population of blight fungi in Europe. pseudonaviculata responsible for the majority of U.S.
It has also been found in numerous nurseries and landscapes in eastern North America.
The disease has been found in several Oregon nurseries (Clackamas, Linn, Marion, Multnomah, Washington, and Yamhill counties) but also in landscapes in Clackamas, Coos, Lane, Multnomah, and Yamhill counties and in Seattle, WA. buxicola) was found for the first time late in 2011 in three Oregon and four British Columbia nurseries.
Cause The fungus Calonectria pseudonaviculata (synonyms Cylindrocladium pseudonaviculatum or C.
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